Stock and Flow Problems
 Last problem was 0480 (HELP)

Q112. Sketch a causal loop diagram representing this logic:

1. …makes you frown…
2. …which makes people avoid you…
3. …which makes you lonely…

Q113. Sketch a causal loop diagram for this system (be sure to label each link and the overall loop). Comment on the long term equilibrium of this system.

• Being happy…
1. …makes you to smile…
2. …makes people approach you…
3. …makes you feel social…
4. …makes you happy…

Q126. Why do people scream into cell phones? Answer in terms of feedback.

Q127. Consider the singles bar scene. Develop a model along the lines of the market for lemons (Wikipedia), that would suggest that information asymmetries could possibly kill the scene. What institutional interventions prevent this from happening?.

Q128. Consider the act of filling up a bathtub for a baby (or yourself!). You have a faucet that you can turn more towards hot or toward cold. List out the flows, the stocks, the sources of information, the "valves," and the rules that govern the valves in this system.

Q129. Draw a stock and flow diagram for filling up a bathtub for a baby (or yourself!). You have a faucet that you can turn more towards hot or toward cold. Be sure to show the flows, the stocks, the sources of information, the "valves," and the rules that govern the valves in this system.

Q130. In a "bathtub problem," why don't we include the water company or the sewer system to be stocks?

Q131. Draw a causal loop diagram that illustrates the process of feeling hungry, eating, becoming satisfied, stopping, getting hungry again.

Q132. Create both a causal loop and a stock and flow diagram for a thermostat, heater, and house. The house is a stock of air. When its temperature goes below some threshold, hot air is added. All along though, hot air is subtracted (or cold air is added) through leaky windows and the like. But the temperature does not change immediately upon introduction of the hot air. What are the challenges of modeling this phenomenon discretely and how can we solve them?

Q133. College is a more or less four year endeavor but students come and go on different schedules. Sketch a stock and flow model that shows freshwomen applicants coming from the cloud, admitted students from applicants, and freshwomen from the admittees. Then freshwomen become sophomores, mostly, but there is some attrition. And so on through the other years. Sketch a stock and flow diagram that follows students through four years and think up some variables that might affect the flows between the different years. For this problem, you should try wearing the hat of an academic administrator who is interested in the problems of "retention" and "degree completion."

Q134. Consider a system for a flu vaccine clinic. People arrive at some random or fixed rate and queue up. Our first station (F) has to get them to fill out a form, sign some papers, etc. After this they get in the line for the actual shots (at station V). We have a fixed number of staff whom we will divide between the two stations, depending on the size of the queues. Draw the stock and flow diagram for the system and write the equations for Q1, Q2, F and V.

Q135. Walk us through this diagram

Q185. Sketch a causal loop diagram for these two systems (be sure to label each link and the overall loop). Comment on the long term equilibrium of this system.

• Being pro candidate X…
1. …makes you give money…
2. …makes the campaign send you emails…
3. …makes you want to go to a rally…
4. …makes pro candidate X…
• Being pro candidate X…
1. …makes you give money…
2. …makes the campaign send you emails…
3. …makes you get fed up with the campaign…
4. …makes you a little sour on candidate X…
• Not hearing much from the campaign…
1. …makes you miss your candidate
2. …makes you feel more pro candidate X

Q188. "Women's issues" have been talked about a lot in the 2012 presidential campaigns. One issue has been the hiring of women in leadership positions in society. Draw a causal loop diagram to represent the following relationships.

The more "gender bias" the fewer qualified women there will be.
More qualified women means more women in positions of power.
The more women in power, the less "gender bias" in society.

Assuming we start with social bias and not many women in positions of power, how is this system likely to behave?

Now let's modify things a bit. Let's suppose we solve the "supply" problem and break the link between bias and the number of qualified women and that the latter grows significantly. We change our model slightly:

Societal bias produces social blindness to existence of qualified women.
This social blindness means fewer women will be in the pool that is considered for positions of power.
The fewer women in the pool, the fewer end up in positions of power.
And, as before, the more (fewer) women in power, the less (more) "gender bias" in society.

Draw this causal model.

Now let's add another causal relation: the fewer women in positions of power, the more NGOs emerge to promote women's participation in government, etc. The NGOs hit on a strategy called that the men in power call "binders of women" — whereby they do the legwork needed to show the men the qualified women that their bias made them blind to.

Add the NGOs and the binders to our causal model. Identify a balancing loop that might portend the achievement of improved gender diversity in positions of power.

Q325. Have a look at the paper shown below about immunization in Uganda. Look especially at the causal loop diagrams on pages 102(146) and 103(147). Explain what is going on in each of the labeled/shaded loops. In some cases, there might be a sign missing. Based on your reading of the diagrams, supply these and explain.

## References

http://www.foundationcoalition.org/resources/ie/Ops1/ops1.ppt

page revision: 65, last edited: 28 Sep 2012 15:58